The present invention relates to a cigarette manufacturing machine.
Cigarette manufacturing machines are known to produce a continuous cigarette rod by feeding a continuous strip of paper, on a conveyor belt, through a loading station where the said strip of paper is loaded with a continuous stream of shredded tobacco.
Together, the paper and tobacco are then fed by the said conveyor through a guide for forming the rod, the said guide generally being defined by a surface along which to run the conveyor, the shape of the said surface first changing from flat to concave in the crosswise direction in relation to the travelling direction of the conveyor, then to cylindrical, thus forcing the said strip of paper to wrap crosswise round the said stream of tobacco.
The continuous rod thus formed is then fed through a crosswise cutting device which cuts the continuous rod at a constant preset rate to form cigarettes or cigarette pieces. On the abovementioned known types of manufacturing machines, the said conveyor belt and the said cutting device are usually driven by a single motor in view of the importance of providing for an extremely precise relationship between the operating speed of the cutting device and the travelling speed of the continuous rod. In fact, if the speed of the cutting device remains constant, any increase or reduction in the travelling speed of the continuous rod in relation to the correct required speed would automatically result in the cigarettes being lengthened or shortened respectively in relation to the required length.
On the abovementioned known types of manufacturing machines, one perfect relationship between the speed of the cutting device and the travelling speed of the rod is usually unachievable on account of the conveyor belt. The latter usually comprises a number of transmission rollers, a drive roller, connected to the said motor, and a belt which is wound round the said rollers and is the main reason for any inaccuracy in the length of the cigarettes produced on the machine. The reason for this is that the dynamic behaviour of different belts is never the same and, more important, even the dynamic behaviour of a single belt changes with time.
Consequently, notwithstanding constant speed on the drive roller, the travelling speed of the belt may vary over time thus resulting in changes to the length of the cigarettes produced on the machine.